Method for fixing light-sensitive free radical photographic materials with heavy metal salts

ABSTRACT

Images formed in free radical photosensitive materials comprising organic halogen-containing photoactivators capable of generating halogen free radicals upon exposure to light are fixed by treatment with aqueous solutions of reducing heavy metal salts.

nited States Patent Inventors Kohel ltano;

Sholchiro Hoshino; Akira Kate, all of Tokyo, Japan Appl. No. 662,591Filed Aug. 23, 1967 Patented Dec. 28, 1971 Assignee Keuflel & Esser Co.

Hoboken, NJ. Priority Aug. 24, 1966 Japan 41/55418 METHOD FOR FIXINGLIGHT-SENSITIVE FREE RADICAL PHOTOGRAPHIC MATERIALS WITH ConciseChemical and Technical Dictionary, page 456, Edited by H. Bennett,published by Chemical Publishing Company, lnc., Brooklyn, New York, 1947Primary Examiner-Norman G. Torchin Assistant Examiner-Richard E. FichterAttorneys-J. Russell .luten, Melford A. Juten, Peter F. Willig andLionel N. White ABSTRACT: images formed in free radical photosensitivematerials comprising organic halogen-containing photoactivators capableof generating halogen free radicals upon exposure to light are fixed bytreatment with aqueous solutions of reducing heavy metal salts.

METHOD IFOR FIXING LIGHT-SENSITIVE FREE RADICAL PHOTOGRAPHIC MATERIALSWITH HEAVY METAL SALTS agent showing a visible color change by action ofsaid free radical is subjected to image wise exposure to form an imageand is then treated with a reducing heavy metal salt. An object of thepresent invention is to provide a fixing method which has no detrimentaleffect on the resulting image, is simple in operation and gives no harmto the human body.

As methods for fixing this kind of light sensitive photographicmaterial, there have heretofore been known a heat fixing method and asolvent fixing method. The heat fixing method is carried out in such amanner that the light sensitive photographic material is subjected toimage wise exposure to form an image and is then heated to decompose orsublimate the composition which has been left without taking part in theimage formation, so that no color change is caused any more even whenthe image is exposed to light.

As light sensitive photographic materials which are effectively treatedaccording to said heat-fixing method, there are those containing a lightsensitive composition composed mainly of diphenylamine and carbontetrabromide or Brilliant green and carbon tetrabromide. Further, as thephotoactivator agents, aroyl trihalogenated hydrocarbons have beenrecommended in addition to carbon tetrabromide. As is well known,however, carbon tetrabromide is extremely toxic and its permissibleamount per day is about 1 p.p.m. Therefore, a special consideration isnecessary so as not to inhale its vapor during the heat treatment. Thus,carbon tetrabromide is not desirable for practical use. Further, aroyltrihalogenated hydrocarbons are strongly lachrymatory and are vaporizedon heating, and therefore they are not desirable as in the case ofcarbon tetrabromide. According to the heat fixing method, lightsensitive photographic materials are heated to decompose or sublimatethe compositions, as mentioned above. Therefore, light sensitivematerials to be treated with this method should contain components whichare readily decomposable and sublimatable. [t is, however, well knownthat ordinarily, components having such properties are more or lessdecomposed or sublimated even at normal temperature. The heat-fixingmethod, therefore, is applicable only to light sensitive photographicmaterials low in storability and is not suitable for those high instorability.

On the other hand, the solvent fixing method is carried out in such amanner that a composition, which has been left without taking part inthe formation of image, extracted with a suitable solvent, so that nocolor change occurs even when the image is reexposed. In this method,therefore, it is necessary to use a solvent which readily dissolves onlythe composition left without taking part in the image formation but doesnot dissolve the formed image at all. If there is used a solvent whichdissolves the image even to a slight extent, the image runs by treatmenttherewith, whereby the reproduction is lowered in resolving power.Therefore, solvents which satisfy the above object are greatlyrestricted and the selection of suitable solvent is extremely difficult.Moreover, the solvent fixing method is a process in which a so-callednonimage portion is washed. Accordingly, in order to effect the washingcompletely, the washing solvent should be used in a large amount orshould be frequently exchanged and a large cost is required therefore.Thus, the solvent fixing method is not practical, either.

The present invention is a fixing method, which has overcome all theabove drawbacks. in the present method, a reducing heavy metal salt isused as a fixing agent, and a light sensitive photographic material,which has been exposed, is either coated with or is immersed in anaqueous solution of said salt. The fixing agent employed in the presentinvention neutralizes by chemical action the activity of anyphotoactivator which has not taken part in the formation of image, andis considered to capture halogens present in the components of theoptically active agent to make said agent inert to light.

Typical compounds as such fixing agents are stannous chloride, stannousbromide, stannous iodide, titanic chloride, ferrous sulfate, titanicsulfate, vanadous sulfate, chromous chloride and chromous sulfate.

According to the present invention, the above-mentioned fixing agent isformed into an aqueous solution at a concentration of about 5-40percent, and a light sensitive photographic material, which has beenexposed, is either coated with or is immersed in said aqueous solution.In the case of coating, the amount of fixing solution to be applied isaffected by the kind of optically active agent and the thickness oflight sensitive layer, but the fixing solution may be applied in such anamount as used in the color development of wet type diazo copying paper,i.e. in such an amount as to wet the surface of the photographic paper,and, in practice, it may be said that the amount is as employed in asemidry diazo process. In this case, the fixing solution may beincorporated with a binder such as a cellulose derivative, vinyl polymeror synthetic rubber. In the case of immersion, the treatment may beeffected in the same manner as in the developing and fixing treatmentsof silver halide light sensitive materials. The concentration of fixingsolution and the treating time are affected by the kind ofphotoactivator and the thickness of light-sensitive layer and are notdefinite. Ordinarily, however, favorable results are obtained when thetreatment is effected for several seconds to several minutes.

In applying the fixing solution onto the surface of a light sensitivephotographic material, the adoption of a somewhat higher concentrationthan in the case of immersion results in more favorable fixing effects.However, if a light sensitive photographic material, which has beencoated with or immersed in the fixing solution, is heated and dried at atemperature of l00-l C. (by means of a hot roll or hot plate having asurface temperature of l00l80C.), the fixing effects are furtherenhanced and the concentration of the fixing solutions can be lowered.

If the fixing solution is incorporated with about 2-20 percent of acompound capable of increasing the reducing ability of the reducingheavy metal salt employed, such as hydrochloric acid, caustic soda oracetic acid, the amount of the fixing agent can advantageously bereduced. Further, if the fixing solution has been incorporated with 2-l5percent of a complex compound-forming agent such as potassium chlorideor potassium iodide, or a buffer agent such as sodium carbonate orborax, the storability (life) of the fixing solution can be prolongedordinarily to several times the life of a fixing solution notincorporated with such compound. According to the present method, thefixing solution is further incorporated with about 2-10 percent of areducing agent such as hydroquinone or metol to prevent the backgroundof image from discoloration due to compounds formed by the fixing.

As mentioned above, the fixing solution employed in the presentinvention may be incorporated with 2 or 3 assistant components.

Examples of useful photoactivators are as follows:

i. Compounds represented by the general formula R-CX wherein R is anaryl, arkyl, aralkyl, aroyl or alkenyl group or a hydrogen or halogenatom; and X is a halogen atom, such as for example, carbontetrachloride, carbon tetrabromide, hexachloroethane, pentabromoethane,p-nitrobenzotribromide, bromotrichloromethane, hexabromoethane,benzotrichloride, iodoform, tetrachlorotetrahydronaphthalene, chloral,bromal,

l, l l -tribromo-2-methyl-2-propanol, l,l ,2,2 tetrabromoethane,2,2,2-tribromoethanol, trichloroacetamide, 1,1 l-trichloro-dimethyl-2-propanol and 11,01,11-

trichlorotoluene.

ii. Compounds represented by the general formula wherein R is a hydrogenatom or 1-5 substituents on the benzene ring, said substituents beingany of nitro, halogen, alkyl, haloalkyl, acetyl, haloacetyl, alkaryl andalkoxy groups, and not all of the substituents are required to be same,such as for example, O-nitro-a,a,a,-tribromoacetophenone,m-nitroa,a,aa,a,atribromoacetophenone,a,,a-m-tetrobromoacetophenonepz,a,a-tribromo-3,4-dichloroacetophenone ,a,a,a-ptetromoacetophenone, anda,a,a,a,a,oz-hexabromo-pdiacetylbenzene.

iii. Compounds represented by the general formula wherein R is an alkylgroup or aryl group (including the case where the group has asubstituent); and X is a halogen atom, such as for example,1,3-benzenesulfonyl chloride, 2,4-dinitrobenzenesulfonyl chloride,o-nitrobenzenesulfonyl chloride, m-nitrobenzenesulfonyl chloride,3,3-diphenylsulfonedisulfonyl chloride, ethanesulfonyl chloride,pbromobenzenesulfonyl chloride, p-nitrobenzenesulfonyl chloride,p-iodobenzenesulfonyl chloride, p-acetamidebenzenesulfonyl chloride,p-toluenesulfonyl chloride, methanesulfonyl chloride, benzenesulfonylchloride, mnitrobenzenesulfonyl fluoride and benzenesulfonyl bromide.

iv. Compounds represented by the general formula wherein R is an alkylgroup or aryl group (including the case where the group has asubstituent and X is a halogen atom); and X is a halogen atom, such asfor example, 2,4- dinitrobenzenesulfinyl chloride ando-nitrobenzenesulfenyl chloride.

V. Compounds represented by the general formula wherein R is asubstituted or unsubstituted aryl group or heterocyclic residue; X X andX are individually a hydrogen, chlorine or bromine atom, and not all ofthem are hydrogen atoms at the same time, such as for example,hexabromodimethyl sulfoxide, pentabromodimethyl sulfoxide,hexabromodimethyl sulfone, trichloromethyl-phenylsulfone,tribromomethyl-phenylsulfone, trichloromethyl-pchlorophenylsulfone,tribromomethyl-p-nitrophenylsulfone,2-trichloromethylbenzothiazolylsulfone-(2),4.6-dimethylpyrimidyl-2-trioromomethylsulfone,tetrobromodimethylsulfone, 2.4-dichlorophenyl-trichloromethylsulfone,2-methyl-4- chlorophenyl-trichloromethylsulfone, 2.5-dimethyl-4-chlorophenyl-trichloromethylsulfone and2.4-dichlorophenyltribromomethylsulfone.

There are generally two kinds of chromotropic agents. One is acolor-forming agent employed as the so-called negativepositive-typewhich originally is a colorless substance but is convertible into acolored state by action of a free radical formed from theabove-mentioned optically active agent. The other is discoloring agentemployed as the so-called positivepositive-type which originally iscolored but, by action of said free radical, the color is changed toanother color or is decolored to colorless. Examples of suchchromotropic agents are amine compounds such as diphenylamine,dibenzylamine, triphenylamine, N-hydroxyethyl-N-ethylaniline and P.P-methylenebis (N,N-diethylaniline); leuco-base dyes such asLeucomalachite green, Michlers hydrol and Leucomethylene Blue; and dyesof the diphenylmethane, triphenylmethane, thiazine, oxazine, xanthene,anthraquinone, iminonaphthoquinone and azomethine types.

Further, there may be included in the photosensitive compositionsadditives such as sensitizers, color tone-improving agents and vehicles,and even in the case of light sensitive photographic materialsincorporated with such additives, the present method effectivelydisplays the fixing effects.

In short, in accordance with the present method, a light sensitivephotographic material which has been exposed may merely be coated withor immersed in an aqueous solution of such fixing agent as mentionedabove and, if necessary, may be heated and dried after fixing. Thepresent method, therefore, is free from such drawbacks as generating apoisonous gas or dissolving an image formed to lower the resolving powerof the image, as seen in the conventional method, i.e. the method inwhich the fixing is effected by mere heating or the solvent fixingmethod in which an expensive solvent is used in a large amount.Accordingly, the operation is effected in a simple manner and excellentstable copies can be formed.

The following examples illustrate the present invention.

EXAMPLE 1 A photographic baryta paper was coated under a red safety lampwith a sensitive liquid having the composition as shown below and wasthen dried.

Hexabromodimethylsulfone 2.5 g. Diphenylaminc 5.0 g. Acetone I00 cc.

On the thus obtained light sensitive photographic material was placed aphotographic negative original sheet, and the material was exposed to a800 w. mercury lamp for 5 seconds at a distance of 5 cm., whereby a deepblue positive image with a white background was obtained.

Subsequently, the photographic material bearing said image was immersedfor one minute in a fixing solution of the composition shown below toobtain a copy entirely stable to light.

Composition of fixing solution:

Stannous chloride 5 8 Hydrochloric acid 1 cc. Water cc.

Further, when the image-bearing photographic material was treated with afixing solution prepared by incorporating 3 g. of hydroquinone to theabove fixing solution, no discoloration in background was seen even whenthe image had been stored for a long period of time.

Example 2 In the same manner as in example 1, a sensitive liquid havingthe composition shown below was applied onto a photographic barytapaper.

w,w,w,-Tribromoquinaldinc 2.5 g. N-Hydroxyethyl-Nethylaniline 5.0 g.Acetone 100 cc.

The thus obtained light sensitive photographic material was exposed inthe same manner as in example I, and was then coated, using a wet-typediazo developing means, with a fixing solution having the compositionshown below to such an extent that the surface of the photographicmaterial was wetted, whereby a blue image entirely stable to reexposurewas obtained.

Stannous bromide l g. Hydrochloric acid 2 cc. Water 100 cc.

Further, when the photographic material in a wet state by application ofthe fixing solution was heated and dried at 150 C. for 7 seconds, theresulting image was stable as in the above case. In this case, however,sufficiently effective fixing could be attained even when there was useda fixing solution having a composition lowered in concentration of thefixing agent as shown below.

Stannous bromide 7 g. Hydrochloric acid 2 cc. Water 100 cc.

Example 3 In the same manner as in example 1, a sensitive liquid havinga composition as shown below was applied onto a photographic barytapaper.

Carbon tetrabromide g. Diphenylamine 5 g. Cellulose acetate 2 g. AcetoneI00 cc The thus obtained light sensitive photographic material wasexposed in the same manner as in example 1 to immediately obtain a blueimage.

Subsequently, the photographic material bearing said image was immersedfor 1 minute in a fixing solution having the composition shown below,whereby the image became stable to reexposure.

Stannous chloride g. Tartaric acid 5 g. Aerosol MA 0.1 cc.

Water I00 cc.

(aerosol MA is an anion surface active agent produced by AmericanCyanamid Co.)

Further, when the above fixing solution was incorporated with 5 g. of ametallic zinc powder, the life of the fixing solution was prolonged toabout 5 times.

Example 4 A white base, which had been surface-treated with a 10 percentaqueous solution of a polyvinyl alcohol having a polymerization degreeof 600, was coated with a sensitive liquid having the composition shownbelow to prepare a bluish green colored light-sensitive photographicmaterial.

Tribromomethylphenylsulfone 5 g. Ethylaminophenyliminonaphthoquinone 2,5g. Cellulose acetate l g. Acetone I00 cc.

Stannous chloride l0 5. Tepol 6l0 0.1 g. Water 100 cc,

Example 5 in the same manner as in example I, a sensitive liquid hav- 1ing the composition as shown below was applied onto a photographicbaryta paper.

Z.5-Dimethyl-4-chlorophenyltrichloromethylsull'one 5 g. Diphenylamine l0g. Acridine Orange 0.1 g. Acetone I00 cc.

The light sensitive photographic material thus obtained contains asensitizing coloring matter and hence is sensitive even to a visible rayzone. Therefore, the photographic material was exposed for 1520 secondsat a distance of 30 cm., using a photographic negative as an originalsheet, by means of a slide projector having a 300 w. tungsten bulb as alight source, whereby a blue positive image was obtained. Using the samemeans as in example 2, the photographic material bearing said image wassubjected to fixing treatment with a fixing solution having thecomposition shown below to obtain a copy having an image entirely stableto reexposure.

Stannous chloride 5 g. Caustic soda l.5 g. Water 100 cc,

Example 6 Ferrous sulfate Water H) g. I00 cc.

What is claimed is:

1. in a process for forming a permanent image which comprises exposingimagewise to a light copy sheet comprising a composition comprising anorganic halogen-containing photoactivator compound responsive to lightexposure to produce halogen free radicals and a chromotropic agentcapable of producing a visible color change by the action of said freeradicals, thereby forming in said composition a visible color-changeimage corresponding to said light-exposure, and treating said materialto render said composition incapable of further color change uponexposure to light, thereby fixing said color-change image; theimprovement which comprises treating said composition after saidimage-wise light-exposure with an aqueous solution of a reducing salt ofa heavy metal selected from the group consisting of tin, titanium, iron,vanadium, and chromium for a time sufficient to render saidphotoactivator incapable of producing said halogen free radicals uponlight-exposure, thereby fixing said color-change image.

2. The improvement according to claim 1 wherein said aqueous solutioncomprises between about 5 and 40 percent of a heavy metal salt selectedfrom the group consisting of stannous chloride, stannous bromide,stannous iodide, titanic chloride, ferrous sulfate, titanic sulfate,vanadous sulfate, chromous chloride and chromous sulfate.

3. The improvement according to claim 2 wherein said aqueous solutionadditionally comprises between about 2 and 10 percent of an organicreducing agent selected from the group consisting of metol andhydroquinone.

4. The improvement according to claim 1 wherein said treating stepcomprises wetting said composition with said aqueous solution and dryingthe resulting wetted composition at a temperature between about l00-l C.

2. The improvement according to claim 1 wherein said aqueous solutioncomprises between about 5 and 40 percent of a heavy metal salt selectedfrom the group consisting of stannous chloride, stannous bromide,stannous iodide, titanic chloride, ferrous sulfate, titanic sulfate,vanadous sulfate, chromous chloride and chromous sulfate.
 3. Theimprovement according to claim 2 wherein said aqueous solutionadditionally comprises between about 2 and 10 percent of an organicreducing agent selected from the group consisting of metol andhydroquinone.
 4. The improvement according to claim 1 wherein saidtreating step comprises wetting said composition with said aqueoussolution and drying the resulting wetted composition at a temperaturebetween about 100* - 180* C.